The present invention relates generally to door latches for automobile and other vehicle applications and, more particularly, to a switch assembly for an electro-mechanical door latch mechanism.
Traditionally, mechanical devices have been used to latch and unlatch closures such as doors, trunks, hoods, lift gates and hatches and the like in automobiles and other vehicles. As a means to reduce the effort that is necessary to operate such closures, it is known to utilize an electro-mechanical door latch mechanism. For example, a user actuated switch can be employed to trigger the release of a mechanical latch. In this regard, an electrical switch is operable to provide an input to a controller for operating the mechanical latch when it is actuated. In addition, modern styling and ergonomic requirements may dictate the physical configuration of the switch. For example, the switch may need to comprise an aesthetically pleasing user actuation component (e.g., a low profile button) that is of adequate size and shape so as to be easily operated by a user under a wide variety of operating conditions in a wide variety of environments.
Known switch technology for such applications generally incorporates a button having a plurality of electrically conductive xe2x80x9cpillsxe2x80x9d that are insert molded within the interior of the top of the button. The pills complete a circuit when the switch is actuated. For example, when the button is depressed, the conductive pills contact electrically conductive xe2x80x9ctracksxe2x80x9d included on a base portion of the switch assembly and short the two electrical inputs to ground. The conductive pills also serve as mechanical xe2x80x9cstopsxe2x80x9d for preventing the button from being further depressed after electrical contact is made.
A known problem that is inherent with the foregoing switch technology, however, is that the several pills do not function independently of one another to ground the electrical input to the switch. Thus, it is possible that the button may be fully depressed, yet the switch is not actuated because the pill or pills do not make adequate contact with both the input and ground side of the electrical tracks. In such a case the pill or pills are brought into contact with only one electrical track. For example, due to the size and/or configuration of the button, it is not uncommon for the button to rock or teeter when an off-center actuation force is applied to depress the button. In such a case only one of the pills is brought into contact with one electrical track. As a result, the reliability of the switch is diminished. In order to address this issue, expensive conducting materials have been used to make the pills. The cost of the switch, though, is correspondingly increased.
Consequently, it is desirable to provide a switching apparatus having a lower cost than conventional switch technology, and with a more reliable actuation mechanism.
A switch assembly for triggering the release of a door latch is disclosed. In an exemplary application for a preferred embodiment of the invention, a switch assembly mounted on the exterior of an automobile door assembly includes an elastomeric button having a plurality of elastomeric posts extending from an inboard surface thereof. An electrically conductive spring plate has a plurality of apertures for accepting the plurality of projections or posts therethrough. The posts interface with the apertures to urge the spring plate into engagement with the inboard surface of the button. A base supports the button and includes a leadframe disposed thereon. The leadframe includes electrically conductive tracks and communicates with a vehicle computer. Depressing the button causes at least a portion of the spring plate to engage the electrically conductive tracks and complete a circuit, initiating the release of the latch.
A method for assembling a switch assembly for triggering the release of a door latch includes providing an elastomeric button having a plurality of elastomeric, generally cylindrical posts extending from an inboard side thereof. An electrically conductive spring plate is provided and includes a plurality of complimentary apertures therein for accepting each of the plurality of elastomeric posts. The spring plate is placed over the inboard side of the button such that the posts are received in and extend through the apertures in the spring plate.
The posts are then loaded in tension in a direction along their respective longitudinal axes. As such, the elastomeric posts stretch and narrow in diameter. The spring plate is simultaneously urged toward the inboard side of the button. The posts are subsequently released from the tensile load and allowed to relax, returning their pre-stretched diameters. The spring plate is further urged into contact with the inboard side of the button. The button is subsequently installed into a base.